ISOLATION AND CHARACTERIZATION OF CHROMATIN FROM NEUROSPORA CRASSA

Different preparations of chromatin isolated from mycelia of Neurospora crassa were analyzed for DNA-associated RNA and proteins. The UV absorption spectra, the ultrastructure of chromatin, and the amino acid composition of the acid-extractable proteins were studied. The protein:DNA ratios range from 1.5 to 2.8; the RNA:DNA ratios range from 0.5 to 1.24. UV absorption shows a macimum at 259 mµ and a minimum at 238–239 mµ. The E280/E260 ranges from 0.59 to 0.70. Electron microscopy reveals a fibrous structure with individual fibers of 120–150 A average diameter. Attempts were made to study the protein by polyacrylamide gel electrophoresis and amino acid analysis. The results indicate that Neurospora chromatin does not contain basic proteins comparable to calf thymus histone. The ratios of basic to acidic amino acids range from 0.93 to 1.19. On electrophoresis, no bands are seen whose positions correspond to those of histones. Staining for basic proteins with fast green or eosin Y at pH 8.2 also shows a negative reaction, suggesting the absence of histones.     

Study of the gametocytocidal/sporontocidal action of qinghaosu (artemisinin) by electron microscopy

The gametocytocidal efficacy of artemisinin (qinghaosu) was evaluated and scanning electron microscopical evidence is given for gametocytocidal action of a single 5-10-mg/kg dose of artemisinin against simian malarial parasite (Plasmodium cynomolgi B). No sporontocidal effect of artemisinin was observed.     

N-isobutyryl-His-Trp-Ala-Val-D-Ala-His-Leu-NHMe (ICI 216140) a potent in vivo antaconist analogue of bombesin/gastrin releasing peptide (BN/GRP) derived from the C-terminal sequence lacking the final methionine residue

The GRP receptor mediated growth response in Swiss 3T3 cells has been used to identify BN/GRP antagonists. Analysis of bombesin antagonism by substance P analogues and by truncated GRP analogues revealed that deletion of the C-terminal methionine residue was important for antagonism. Des-Met analogues showing potent antagonist activity in the in vitro 3T3 system (IC50 approximately 2nM) were synthesized. Further structural modification of these peptides led to the identification of (CH3)2CHCO-His-Trp-Ala-Val-D-Ala-His-Leu-NHCH3 (ICI 216140) which reduced bombesin-stimulated rat pancreatic amylase secretion to basal levels when administered subcutaneously at 2.0 mg per kg.     

Somatic embryogenesis and plant regeneration from leaf derived callus of winged bean [Psophocarpus tetragonolobus (L.) DC.]

Somatic embryos were obtained from callus cultures derived from leaf explants of the winged bean, Psophocarpus tetragonolobus (L.) DC. Initiation and development of the somatic embryos occurred with a two-step culture method. Callus cultures initiated on MS medium with NAA and BAP, upon transfer to a new medium with IAA and BAP, produced somatic embryos. Maximum embryogenesis of 60% was obtained on induction medium with 0.5 mg/l NAA plus 1.0 mg/l BAP followed by transfer to a secondary medium with 0.1 mg/l IAA and 2.0 mg/l BAP. Optimal embryo germination and plantlet development was achieved on MS medium with 0.2 mg/l BAP plus 0.1 mg/l IBA. The regenerated plants were successfully transferred to glasshouse conditions.Abbreviations MS Murashige and Skoog (1962) medium - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - IAA Indole-3-acetic acid - IBA Indole-3-butyric acid - BAP 6-benzylaminopurine - KN Kinetin     

Sublethal malathion induced changes in the ovary of an air-breathing fish,Heteropneustes fossilis: a histological study

This paper describes effects of a sublethal (1.2 mg 1^–1) organophosphate, malathion, on the ovary of an air breathing catfish, Heteropneustes fossilis. The study focuses on microscopic changes that occur on ovigerous lamellae, oocytes at different stages of development and the nucleus of the immature oocyte. Also, change in estrogen levels in blood serum is investigated. Clumping of cytoplasm appears after 24 h of exposure to malathion. Clumping intensified after 48 h. Degeneration in the follicular cells was also observed. After 72 h exposure the number of nucleoli increased, nuclear materials shrunk, oocytes became adhered. With 96 h of exposure, nuclear materials of all the oocytes shrunk to a smaller clump. The oocytes fused together, and follicular epithelium became loose and ruptured. A few atretic oocytes were visible. Radioimmunoassay of the estrogen level in blood serum after 72 h of exposure of malathion showed a reduction in the level. This study showed that the histopathological condition of the gonad is reflected in malfunctioning of the endocrine system and hormonal disbalance.     

Structural insights into thermostable direct hemolysin of Vibrio parahaemolyticus using single-particle cryo-EM

Thermostable direct hemolysin (TDH) is a ~19 kDa, hemolytic pore-forming toxin from the gram-negative marine bacterium Vibrio parahaemolyticus, one of the causative agents of seafood-borne acute gastroenteritis and septicemia. Previous studies have established that TDH exists as a tetrameric assembly in physiological state; however, there is limited knowledge regarding the molecular arrangement of its disordered N-terminal region (NTR)—the absence of which has been shown to compromise TDH's hemolytic and cytotoxic abilities. In our current study, we have employed single-particle cryo-electron microscopy to resolve the solution-state structures of wild-type TDH and a TDH construct with deletion of the NTR (NTD), in order to investigate structural aspects of NTR on the overall tetrameric architecture. We observed that both TDH and NTD electron density maps, resolved at global resolutions of 4.5 and 4.2 Å, respectively, showed good correlation in their respective oligomeric architecture. Additionally, we were able to locate extra densities near the pore opening of TDH which might correspond to the disordered NTR. Surprisingly, under cryogenic conditions, we were also able to observe novel supramolecular assemblies of TDH tetramers, which we were able to resolve to 4.3 Å. We further investigated the tetrameric and inter-tetrameric interaction interfaces to elaborate upon the key residues involved in both TDH tetramers and TDH super assemblies. Our current structural study will aid in understanding the mechanistic aspects of this pore-forming toxin and the role of its disordered NTR in membrane interaction.     

Antioxidant and Antidiabetic Properties of Extracts from Three Underutilized Food Plants of North East India

Three underutilized leafy vegetables Sarcochlamys pulcherrima (Roxb.) Gaudich (SP), Ipomoea aquatica Forssk. (IA) and Zanthoxylum rhetsa (Roxb.) DC (ZR) were extracted with different solvents viz. 95 % ethyl alcohol, methanol and hot water. The extracts were evaluated for their antioxidant potential via DPPH, ABTS and FRAP assay along with electroanalytical studies using cyclic voltammetry. The antidiabetic potential was determined by recording their α-amylase and α-glucosidase inhibitory assay. The total phenolic content (TPC), total flavonoid content (TFC) and the liquid chromatography-mass spectrometry (LC/MS) based phytochemical profiles of the extracts were also determined. All three extracts of SP exhibited significant antioxidant capacity. The antidiabetic potential of the IA and ZR extracts was found to be higher than or at par with that of standard acarbose. LC/MS studies reveal the presence of hitherto reported antioxidant and antidiabetic compounds like gamma-aminobutyric acid, cinnamic acid, caffeic acid, α-viniferin, piperlonguminine, niacin, kaempferol, etc., in the extracts.     

Growth, proline accumulation and water relations of NaCl-selected and non-selected callus lines of Dactylis glomerata L

Sodium chloride-tolerant calli were selected from leaf-derived embryogenic calli of Dactylis glomerata L. on agar solidified medium supplemented with 200 mM NaCl, a concentration lethal to non-selected calli. Growth characteristics, water relations and proline accumulation pattern were compared in selected and non-selected lines. The objective was to gain an understanding of the mechanism(s) of tolerance in the NaCl-tolerant line. Growth in the selected line, as expressed in terms of tolerance index (ratio of fresh wt. on NaCl medium:fresh wt. on NaCl free medium x 100), was greater than that of the non-selected line at all levels of NaCl between 50 and 300 mM. There was no significant difference in proline accumulation in the selected and non-selected lines. Maintenance of turgor by osmotic adjustment was observed in the non-selected line despite decreased growth. In contrast, the selected line lost either the need or the ability to adjust osmotically. There was little or no increase in symplastic osmolality in the selected line when exposed to NaCl. Presumably, selection was made for a salt-excluding tissue that has lost the ability to accumulate solutes and adjust turgor with NaCl stress.